1. Field of the Invention
The present invention relates to an electric motor provided with an oil seal for closing a hole for motor airtightness testing.
2. Description of the Related Art
Electric motors used in machine tools, industrial equipment, or industrial robots are expected to be highly oil-resistant and drip-proof, and moreover, they must be highly airtight. For airtightness check or testing of a motor being manufactured, a positive or negative pressure is applied to the interior of the motor to check for air leakage to the outside or air inflow, or an oil seal is removed to allow the motor to be internally pressurized.
Japanese Patent Application Laid-Open No. 2010-31837 discloses a technique for reliably preventing water penetration into a bearing that supports a horizontal motor shaft of a pump unit. In this pump unit, a motor housing and pump housing are formed with a shaft-supporting diaphragm between them. The shaft-supporting diaphragm holds an oil seal on the pump-housing side, and a cylinder section is disposed on the motor-housing side.
In general, a bearing is located in a region from which the oil seal is removed. If this bearing is not airtight, air passes through it, so that airtightness testing can be performed without problems. If the bearing used is furnished with a highly airtight seal, in contrast, a hole for air passage must be separately provided such that it can be closed by a plug or the like after airtightness testing is finished. Thus, in the airtightness testing for the case where the highly airtight bearing is used, the component needed to close the hole causes an increase in the number of components and assembly man-hours.